Trailers of the type wherein the trailer tongue is supported by the towing vehicle require a jack stand to support the tongue and trailer frame in a horizontal position when not attached to a vehicle. This is performed by retractable jack stands, also referred to as “trailer jacks”, which are attached to the tongue, proximate to the trailer hitch. Trailer jacks on small single axle trailers have a foot plate or a single caster wheel mounted at the lower distal end of the jack. Larger weight capacity trailer jacks typically have a single foot plate which serves as the static support for the trailer tongue when the trailer is parked and unhitched. The smaller trailer jacks with casters are functional only to move the trailer without a load on it, or for very limited movement with a load to facilitate hooking up to a hitch. With the trailer loaded, the total weight is too great for manual movement upon the trailer main wheels and the jack caster.
Some attempts have been made to power trailer jack caster wheels to enable movement of a trailer when loaded. This is advantageous for maneuvering for hook-up with a hitch or maneuvering for parking. It is also advantageous to combine the functions of the jack stand with the mechanical powering of the caster or other translation devices or mechanisms.
Many jack stands are constructed with an external sleeve or housing, such as a steel tube, which is statically mounted to the trailer tongue. The external sleeve houses a screw jack assembly which is coupled to the stand which extends from the housing by operation of the jack. The foot plate or caster is attached to the lower distal end of the of the jack. In another trailer jack design, an external sleeve or housing carries an external gear rack which is mounted to the trailer tongue and engaged with a worm gear operable to raise and lower the jack stand relative to the trailer tongue. This design leaves the interior of the sleeve available for an additional shaft which can be used as a drive and steering shaft for a caster wheel mounted at the lower distal end of the sleeve.
Some of the problems with adding these mechanics to the standard trailer jack include the necessity of more complex housings and mountings. Also, the desirability of a larger wheel and tire in place of a single piece caster wheel requires a larger mounting fork, which then interferes with the retraction of the jack as required for the trailer in the traveling configuration. Satisfactory and economic engineering solutions to these challenges have not been provided.